Comment 4 for bug 1946318

Reviewed: https://review.opendev.org/c/openstack/neutron/+/813610
Committed: https://opendev.org/openstack/neutron/commit/a278c5ba789c014ec777a75fc9538179d6707202
Submitter: "Zuul (22348)"
Branch: master

commit a278c5ba789c014ec777a75fc9538179d6707202
Author: Lucas Alvares Gomes <email address hidden>
Date: Tue Oct 12 11:42:39 2021 +0100

    [OVN] Tune OVN routers to reduce the mem footprint for ML2/OVN

    In order to avoid having a MAC_Binding table explosion and helping
    lowering the memory footprint when using ML2/OVN this patch is setting
    two options to the OVN routers:

    * always_learn_from_arp_request: By setting this to False we
      avoid learning from ARP replies observed in the network. Only the
      ARP requests sent by OVN will generate a MAC_Binding entry in the
      OVSDB database. For larger broadcasts domains this avoids having a
      MAC_Binding table explosion, reduce the DB size and memory footprint
      of ML2/OVN.

    * dynamic_neigh_routers: By setting this to True we avoid
      pre-populating flows for router to router communication, reduding
      the number of flows, DB size and memory footprint of ML2/OVN.

    For more information on these option for core OVN please refer to:
    https://www.ovn.org/support/dist-docs/ovn-nb.5.html

    This patch also includes a new maintenance task to include these options
    to existing routers in the system.

    Related-Bug: #1946318
    Change-Id: I056acdec9b6ee2341d2bc4f7bd9a678f3bf91972
    Signed-off-by: Lucas Alvares Gomes <email address hidden>